Saturated linear polyfluorohydrocarbons, processes for their production, and their use in cleaning compositions

ABSTRACT

The compounds CF 3  CHFCHFCF 2  CF 3 , CF 3  CH 2  CHFCF 2  CF 3 , CF 3  CHFCH 2  CF 2  CF 3 , CF 3  CHFCHFCF 2  CF 2  CF 3 , CF 3  CH 2  CHFCF 2  CF 2  CF 3 , CF 3  CHFCH 2  CF 2  CF 2  CF 3 , CF 3  CF 2  CH 2  CHFCF 2  CF 3 , CF 3  CF 2  CHFCHFCF 2  CF 2  CF 3 , CF 3  CHFCHFCF 2  CF 2  CF 2  CF 3 , CF 3  CHFCH 2  CF 2  CF 2  CF 2  CF 3 , CF 3  CH 2  CHFCF 2  CF 2  CF 2  CF 3 , CF 3  CF 2  CHFCH 2  CF 2  CF 2  CF 3 , and CF 3  CF 2  CH 2  CHFCF 2  CF 2  CF 3  ; and compositions thereof. Catalytic processes using Group VIII metals are disclosed for reacting selected olefinic starting materials with hydrogen to produce as the major products dihydropolyfluoroalkanes or trihydropolyfluoroalkanes wherein the hydrogens are positioned on two adjacent carbon atoms; as are processes using iodine and/or hydrogen iodide in the reduction of selected olefinic starting materials to dihydropolyfluoroalkanes or trihydropolyfluoroalkanes.

This is a division of application Ser. No. 07/595,840, filed Oct. 11,1990 now U.S. Pat. No. 5,171,902.

FIELD OF THE INVENTION

This invention relates to fluorine-substituted hydrocarbon compounds,their production, and their use for cleaning solid surfaces, and moreparticularly to polyfluoropentanes, polyfluorohexanes, andpolyfluoroheptanes, their production by the reduction ofpolyfluoroolefin starting materials, and their use as solvents.

BACKGROUND OF THE INVENTION

Various organic solvents have been used as cleaning liquids for theremoval of contaminants from contaminated articles and materials.Certain fluorine-containing organic compounds such as1,1,2-trichloro-1,2,2-trifluoroethane have been reported as useful forthis purpose, particularly with regard to cleaning organic polymers andplastics which may be sensitive to other more common and more powerfulsolvents such as trichloroethylene or perchloroethylene. Recently,however, there have been efforts to reduce the use of certain compoundssuch as trichlorotrifluoroethane which also contain chlorine because ofa concern over their potential to deplete ozone, and to thereby affectthe layer of ozone that is considered important in protecting theearth's surface from ultraviolet radiation.

Boiling point, flammability and solvent power can often be adjusted bypreparing mixtures of solvents. For example, certain mixtures of1,1,2,-trichloro-1, 2,2-trifluoroethane with other solvents (e.g.,isopropanol and nitromethane) have been reported as useful in removingcontaminants which are not removed by1,1,2-trichloro-1,2,2-trifluoroethane alone, and in cleaning articlessuch as electronic circuit boards where the requirements for a cleaning.solvent are relatively stringent, (i.e., it is generally desirable incircuit board cleaning to use solvents which have low boiling points,are non-flammable, have low toxicity, and have high solvent power sothat flux such as rosin and flux residues which result from solderingelectronic components to the circuit board can be removed without damageto the circuit board substrate).

While boiling, flammability, and solvent power can often be adjusted bypreparing mixtures of solvents, the utility of the resulting mixturescan be limited for certain applications because the mixtures fractionateto an undesirable degree during use. Mixtures can also fractionateduring recovery, making it more difficult to recover a solvent mixturewith the original composition. Azeotropic compositions, with theirconstant boiling and constant composition characteristics, are thusconsidered particularly useful.

Azeotropic compositions exhibit either a maximum or minimum boilingpoint and do not fractionate upon boiling. These characteristics arealso important in the use of the solvent compositions in certaincleaning operations, such as removing solder fluxes and flux residuesfrom printed circuit boards. Preferential evaporation of the morevolatile components of the solvent mixtures, which would be the case ifthe mixtures were not azeotropes, or azeotrope-like, would result inmixtures with changed compositions which may have less desirableproperties (e.g., lower solvency for contaminants such as rosin fluxesand/or less inertness toward the substrates such as electricalcomponents).

Azeotropic characteristics are also desirable in vapor degreasingoperations where redistilled material is usually used for finalrinse-cleaning. Thus, the vapor defluxing or degreasing system acts as astill. Unless the solvent composition exhibits a constant boiling point(i.e., is an azeotrope or is azeotropelike) fractionation will occur andundesirable solvent distribution may act to upset the safety andeffectiveness of the cleaning operation.

A number of azeotropic compositions based upon halohydrocarbonscontaining fluorine have been discovered and in some cases used assolvents for the removal of solder fluxes and flux residues from printedcircuit boards and for miscellaneous vapor degreasing applications. Forexample, U.S. Pat. No. 2,999,815 discloses the azeotrope of1,1,2-trichloro-1,2,2-trifluoroethane with acetone; U.S. Pat. No.3,903,009 discloses a ternary azeotrope of1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane and ethanol;U.S. Pat. No. 3,573,213 discloses an azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane; U.S. Pat. No. 3,789,006 disclosesthe ternary azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane withnitromethane and isopropanol; U.S. Pat. No. 3,728,268 discloses theternary azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane with acetoneand ethanol; U.S. Pat. No. 2,999,817 discloses the binary azeotrope of1,1,2-trichloro-1,2,2-trifluoroethane and methylene chloride (i.e.,dichloromethane ); and U.S. Pat. No. 4,715,900 discloses ternarycompositions of trichlorotrifluoroethane, dichlorodifluoroethane, andethanol or methanol.

As noted above, many solvent compositions which have proven useful forcleaning contain at least one component which is a halogen-substitutedhydrocarbon containing chlorine, and there have been concerns raisedover the ozone depletion potential of halogen-substituted hydrocarbonswhich contain chlorine. Efforts are being made to develop compositionswhich may at least partially replace the chlorine containing componentswith other components having lower potential for ozone depletion.Azeotropic compositions of this type are of particular interest.

Means of synthesizing various fluorine-substituted alkanes have beenreported.

U.S. Pat. No. 2,550,953 discloses catalytic hydrogenation of unsaturatedfluorohydrocarbons.

U.S. Pat. No. 2,844,636 discloses that 1,1,2,3,4,4-hexafluorobutene canbe made by reacting perfluorocyclobutene with hydrogen, using elementaliodine as the catalyst.

V. A. Grinberg et al., Bulletin of the Academy of Sciences of the USSR,Division of Chemical Science, 988 (1979) report the synthesis of3,4-dihydro perfluorohexane, CF₃ CF₂ CHFCHFCF₂ CF₃, by theelectrochemical reaction of trifluoroacetic acid, sodiumtrifluoroacetate and trifluoroethylene in aqueous acetonitrile as 5% ofa three-component mixture that was isolated in 30% of the theoretical(based on current) amount.

V. F. Snegirev et al., Izvestiya Akademii Nauk SSSR, SeriyaKhimicheskaya, 1983, No 12, pp. 2775-2781, report the reduction of thebranched perfluoroolefins, perfluoro-4-methyl-2-pentene andperfluoro-2-methyl-2-pentene to mono-, di- and trihydro derivatives bymetal hydride complexes or by hydrogenation over a palladium/carboncatalyst.

J. Li et al., Youji Huaxue, 1984, 40-2, p. 24, report the palladium onalumina catalyzed hydrogenation of hexaftuoropropylene dimers to givedihydro and trihydro reduction products.

I. L. Knunyants et al., Izvestiya Akademii Nauk SSSR, OtdelenieKhimicheskikh Nauk, 1960, No 8, pp. 1412-1418 discusses the catalytichydrogenation of perfluoroethylene, propene and butenes.

U.S. Pat. No. 4,902,839 discloses certain tetrahydro derivatives ofperfluorobutanes, perfluoropentanes and perfluorohexanes, as well asprocesses for their preparation.

SUMMARY OF THE INVENTION

In accordance with this invention, novel compounds are provided whichcontain no chlorine and which may be used alone or in combination withother miscible solvents (e.g., alcohols, ethers, esters, ketones,nitrogen-containing organic compounds such as acetonitrile andnitromethane, and halogenated hydrocarbons) as agents for cleaning solidsurfaces.

The novel compounds of this invention include the group of lineardihydro and trihydro polyfluoropentanes, polyfluorohexanes andpolyfluoroheptanes represented by the structural formulae CF₃ CHFCHFCF₂CF₃, CF₃ CH₂ CHFCF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₃, CF₃CH₂ CHFCF₂ CF₂ CF₂, CF₃ CHFCH₂ CF₂ CF₂ CF₃, CF₃ CF₂ CH₂ CHFCF₂ CF₃, CF₃CF₂ CHFCHFCF₂ CF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₂ CF₂CF₃, CF₃ CH₂ CHFCF₂ CF₂ CF₂ CF₃, CF₃ CF₂ CHFCH₂ CF₂ CF₂ CF₃, and CF₃ CF₂CH₂ CHFCF₂ CF₂ CF₃.

A process is provided in accordance with this invention for preparing alinear trihydropolyfluoroalkane selected from the group consisting ofCF₃ CH₂ CHFCF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₃, CF₃ CH₂ CHFCF₂ CF₂ CF₃, CF₃CHFCH₂ CF₂ CF₂ CF₃, CF₃ CF₂ CH₂ CHFCF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₂ CF₂ CF₃,CF₃ CH₂ CHFCF₂ CF₂ CF₂ CF₃, CF₃ CF₂ CHFCH₂ CF₂ CF₂ CF₃, and CF₃ CF₂ CH₂CHFCF₂ CF₂ CF₃, which comprises the step of reacting an olefinicstarting material in the liquid phase with hydrogen over a Group VIIImetal catalyst (preferably in the presence of a polar solvent); whereinsaid olefinic starting material has the same number of carbon atoms assaid trihydropolyfluoroalkane and is selected from the group ofperfluoroolefins consisting of CF₃ CF═CFCF₂ CF₃, CF₃ CF═CFCF₂ CF₂ CF₃,CF₃ CF₂ CF═CFCF₂ CF₃, CF₃ CF₂ CF═CFCF₂ CF₂ CF₃, and CF₃ CF═CFCF₂ CF₂ CF₂CF₃ ; and wherein .said olefinic starting material has its olefinic bondbetween the carbon atoms which correspond to the carbons which bear thehydrogen in said trihydropolyfluoroalkane.

Another process is provided in accordance with this invention forpreparing a linear trihydropolyfluoroalkane selected from the groupconsisting of CF₃ CH₂ CHFCF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₃, CF₃ CH₂ CHFCF₂ CF₂CF₃, CF₃ CHFCH₂ CF₂ CF₂ CF₃, CF₃ CF₂ CH₂ CHFCF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₂CF₂ CF₃, CF₃ CH₂ CHFCF₂ CF₂ CF₂ CF₃, CF₃ CF₂ CHFCH₂ CF₂ CF₂ CF₃, and CF₃CF₂ CH₂ CHFCF₂ CF₂ CF₃, which comprises the step of reacting an olefinicstarting material at an elevated temperature with hydrogen in thepresence of at least one material selected from the group consisting ofiodine and hydrogen iodide or with hydrogen iodide; wherein saidolefinic starting material has the same number of carbon atoms as saidtrihydropolyfluoroalkane and is selected from the group consisting ofCF₃ CH═CFCF₂ CF₃, CF₃ CF═CHCF₂ CF.sub. 3, CF₃ CH═CFCF₂ CF₂ CF₃, CF₃CF═CHCF₂ CF₂ CF₃, CF₃ CF₂ CH═CFCF₂ CF₃, CF₃ CF₂ CH═CFCF₂ CF₂ CF₃, CF₃CF₂ CF═CHCF₂ CF₂ CF₃, CF₃ CH═CFCF₂ CF₂ CF₂ CF₃, and CF₃ CF═CHCF₂ CF₂ CF₂CF₃ ; and wherein said olefinic starting material has its olefinic bondbetween the carbon atoms which correspond to the carbons which bear thehydrogen in said trihydropolyfluoroalkane.

In accordance with this invention a process is also provided forpreparing a linear dihydropolyfluoroalkane selected from the groupconsisting of CF₃ CHFCHFCF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₃, CF₃ CF₂CHFCHFCF₂ CF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₂ CF₃, and CF₃ CF₂ CHFCHFCF₂ CF₃,which comprises the step of reacting an olefinic starting material inthe vapor phase with hydrogen over a Group VIII metal catalyst; whereinsaid olefinic starting material has the same number of carbon atoms assaid dihydropolyfluoroalkane and is selected from the group consistingof CF₃ CF═CFCF₂ CF₃, CF₃ CF═CFCF₂ CF₂ CF₃, CF₃ CF₂ CF═CFCF₂ CF₃, CF₃ CF₂CF═CFCF₂ CF₂ CF₃, and CF₃ CF═CFCF₂ CF₂ CF₂ CF₃ ; and wherein saidolefinic starting material has its olefinic bond between the carbonatoms which correspond to the carbons which bear the hydrogen in saiddihydropolyfluoroalkane.

Another process is provided in accordance with this invention forpreparing a linear dihydropolyfluoroalkane selected from the groupconsisting of CF₃ CHFCHFCF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₃, CF₃ CF₂CHFCHFCF₂ CF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₂ CF₃, and CF₃ CF₂ CHFCHFCF₂ CF₃,which comprises the step of reacting an olefinic starting material inthe liquid phase with hydrogen over a Group VIII metal catalyst(preferably in the absence of a polar solvent); wherein said olefinicstarting material has the same number of carbon atoms as saiddihydropolyfluoroalkane and is selected from the group consisting of CF₃CF═CFCF₂ CF₃, CF₃ CF═CFCF₂ CF₂ CF₃, CF₃ CF₂ CF═CFCF₂ CF₃, CF₃ CF₂CF═CFCF₂ CF₂ CF₃, and CF₃ CF═CFCF₂ CF₂ CF₂ CF₃ ; and wherein saidolefinic starting material has its olefinic bond between the carbonatoms which correspond to the carbons which bear the hydrogen in saiddihydropolyfluoroalkane.

A third process is provided in accordance with this invention forpreparing a linear dihydropolyfluoroalkane selected from the groupconsisting of CF₃ CHFCHFCF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₃, CF₃ CF₂CHFCHFCF₂ CF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₂ CF₃, and CF₃ CF₂ CHFCHFCF₂ CF₃,which comprises the step of reacting an olefinic starting material at anelevated temperature with hydrogen in the presence of at least onematerial selected from the group consisting of iodine and hydrogeniodide or with hydrogen iodide; wherein said olefinic starting materialhas the same number of carbon atoms as said dihydropolyfluoroalkane andis selected from the group consisting of CF₃ CF═CFCF₂ CF₃, CF₃ CF═CFCF₂CF₂ CF₃, CF₃ CF₂ CF═CFCF₂ CF₃,CF₃ CF₂ CF═CFCF₂ CF₂ CF₃,and CF₃ CF═CFCF₂CF₂ CF₂ CF₃ ; and wherein said olefinic starting material has itsolefinic bond between the carbon atoms which correspond to the carbonswhich bear the hydrogen in said dihydropolyfluoroalkane.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides novel saturated linear polyfluorohydrocarbons(i.e., polyfluoroalkanes) which contain two or three hydrogen atoms permolecule. The trihydropolyfluoroalkanes of this invention include thetrihydropolyfluoropentanes represented by the structural formulae CF₃CH₂ CHFCF₂ CF₃, and CF₃ CHFCH₂ CF₂ CF₃ ; the trihydropolyfluorohexanesrepresented by the structural formulae CF₃ CH₂ CHFCF₂ CF₂ CF₃, CF₃CHFCH₂ CF₂ CF₂ CF₃, and CF₃ CF₂ CH₂ CHFCF₂ CF₃ ; and thetrihydropolyfluoroheptanes represented by the structural formulae CF₃CHFCH₂ CF₂ CF₂ CF₂ CF₃, CF₃ CH₂ CHFCF₂ CF₂ CF₂ CF₃, CF₃ CF₂ CHFCH₂ CF₂CF₂ CF₃, and CF₃ CF₂ CH₂ CHFCF₂ CF₂ CF₃.

A process is provided in accordance with this invention for preparingthese trihydropolyfluoroalkanes which comprises the step of reacting anolefinic starting material in the liquid phase with hydrogen over aGroup VIII metal catalyst, preferably from the palladium group (i.e.,Pd, Rh and/or Ru). Palladium and rhodium are the more preferred metals,with palladium being most preferred. The metal catalyst may besupported, for example on carbon or on alumina. The olefinic startingmaterial used for this process has the same number of carbon atoms asthe desired trihydropolyfluoroalkane and is selected from the group ofperfluoroolefins consisting of CF₃ CF═CFCF₂ CF₃, CF₃ CF═CFCF₂ CF₂ CF₃,CF₃ CF₂ CF═CFCF₂ CF₃, CF₃ CF₂ CF═CFCF₂ CF₂ CF₃, and CF₃ CF═CFCF₂ CF₂ CF₂CF₃. Thus, a polyfluoroalkane selected from the group consisting of CF₃CH₂ CHFCF₂ CF₃ and CF₃ CHFCH₂ CF₂ CF₃ can be produced by hydrogenatingCF₃ CF═CFCF₂ CF₃ over a metal catalyst in accordance with thisinvention; a polyfluoroalkane selected from the group consisting of CF₃CH₂ CHFCF₂ CF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₂ CF₃, and CF₃ CF₂ CH₂ CHFCF₂ CF₃can be produced by hydrogenating a starting material selected from thegroup consisting of CF₃ CF═CFCF₂ CF₂ CF₃ and CF₃ CF₂ CF═CFCF₂ CF₃ over ametal catalyst in accordance with this invention; and a polyfluoroalkaneselected from the group consisting of CF₃ CHFCH₂ CF₂ CF₂ CF₂ CF₃, CF₃CH₂ CHFCF₂ CF₂ CF₂ CF₃, CF₃ CF₂ CHFCH₂ CF₂ CF₂ CF₃ and CF₃ CF₂ CH₂CHFCF₂ CF₂ CF₃ can be produced by hydrogenating a starting materialselected from the group consisting of CF₃ CF₂ CF═CFCF₂ CF₂ CF₃ and CF₃CF═CFCF₂ CF₂ CF₂ CF₃ over a metal catalyst in accordance with thisinvention. In any case the olefinic starting material should have itsolefinic bond between the carbon atoms which correspond to the carbonswhich bear the hydrogen in the desired trihydropolyfluoroalkane.

The reduction can be carried out at temperatures in the range of fromabout 0° C. to about 200° C. The preferred temperature range is fromabout 25° C. to about 100° C. The pressure of the hydrogenation may bewithin a wide range, from less than 1 atmosphere to extremely highpressures, but normally pressures from 1 atmosphere to about 10atmospheres is preferred. The molar ratio of hydrogen to olefinicstarting material for this process is preferably between about 1:1 and100:1; and is more preferably between about 2:1 and 10:1. For batchprocesses, the hydrogen may be provided by continuous or intermittentaddition to a reactor containing the olefinic starting material and thecatalyst until the desired ratio (based upon the initial amount ofstarting material) is attained.

The hydrogenation is preferably conducted in the presence of a polarsolvent. The presence of a polar solvent is essential for highselectivity to the trihydro derivatives from the perfluoroolefinstarting materials. Suitable polar solvents which may be employedinclude water, alcohols, glycol, acetic acid, dimethylformamide,N-methyl pyrollidone and triethylamine, or mixtures thereof. Methanol isa preferred polar solvent.

The olefinic starting materials for this process may be prepared inaccordance with the teachings of U.S. patent application Ser. No.07/595,839 (see U.S. Pat. No.5,162,594 which issued pursuant to acontinuation-in-part thereof), which is hereby incorporated by referencein its entirety. According to the teachings therein, polyfluoroolefinshaving at least 5 carbon atoms may be manufactured by reacting togethertwo selected polyfluoroolefins in the presence of a catalyst of theformula AlX₃ where X is one or more of F, Cl or Br (provided that X isnot entirely F). As exemplified by Example A herein, a five carbonperfluoroolefinic starting material may be prepared by the reaction ofhexafluoropropene (HFP) with tetrafluoroethylene (TFE). Six carbonperfluoro-olefinic starting materials may be prepared by the reaction,substantially according to the procedure of Example A, of1,1,1,4,4,4-hexafluoro-2,3-dichloro-2-butene with TFE to yield anintermediate product comprising perfluoro-2,3-dichloro-2-hexene whichmay then be converted to a mixture of perfluoro-2-hexene andperfluoro-3-hexene by reaction with potassium fluoride in refluxingN-methyl pyrolidone. A mixture of seven carbon perfluoroolefinicstarting materials may be prepared by the reaction, substantiallyaccording to the procedure of Example A, of hexafluoro-propene with 2moles of TFE.

Another process is provided in accordance with this invention forpreparing a linear trihydropolyfluoroalkane selected from the groupconsisting of CF₃ CH₂ CHFCF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₃, CF₃ CH₂ CHFCF₂ CF₂CF₃, CF₃ CHFCH₂ CF₂ CF₂ CF₃, CF₃ CF₂ CH₂ CHFCF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₂CF₂ CF₃, CF₃ CH₂ CHFCF₂ CF₂ CF₂ CF₃, CF₃ CF₂ CHFCH₂ CF₂ CF₂ CF₃, and CF₃CF₂ CH₂ CHFCF₂ CF₂ CF₃, which comprises the step of reacting an olefinicstarting material at an elevated temperature with hydrogen in thepresence of at least one material selected from the group consisting ofiodine and hydrogen iodide or with hydrogen iodide; wherein saidolefinic starting material has the same number of carbon atoms as saidtrihydropolyfluoroalkane and is selected from the group consisting ofCF₃ CH═CFCF₂ CF₃, CF₃ CF═CHCF₂ CF.sub. 3, CF₃ CH═CFCF₂ CF₂ CF₃, CF₃CF═CHCF₂ CF₂ CF₃, CF₃ CF₂ CH═CFCF₂ CF₃, CF₃ CF₂ CH═CFCF₂ CF₂ CF₃, CF₃CF₂ CF═CHCF₂ CF₂ CF₃, CF₃ CH═CFCF₂ CF₂ CF₂ CF₃, and CF₃ CF═CHCF₂ CF₂ CF₂CF₃ ; and wherein said olefinic starting material has its olefinic bondbetween the carbon atoms which correspond to the carbons which bear thehydrogen in said trihydropolyfluoroalkane. The hydrogen-containingolefinic starting materials may be made substantially according to theprocedure of Example A, but using monohydro compounds rather thanperfluoro compounds (e.g., 2H-pentafluoropropene rather than HFP).

Iodine and/or HI is used for this hydrogenation in accordance with theteachings of U.S. patent application Ser. No. 07/533,333 (see U.S. Pat.No. 5,097,082 which issued pursuant to a continuation-in-part thereof).Hydrogen iodide for the reaction may be provided by several methods. Forexample, the reaction may be run with stoichiometric HI. Alternatively,the reaction may be run with catalytic amounts of HI in the presence ofhydrogen. The reaction may also be run with hydrogen using catalyticamounts of iodine. This latter method is preferred for batch reactionsand for ease of handling. This reaction may be accomplished in theabsence of supported metal catalysts; and indeed the catalyst for thisreaction typically consists essentially of iodine and/or hydrogeniodide. The reaction temperature for this reaction should generally befrom 100° C. to 500° C. A preferred temperature range is from 200° C. to400° C. This reaction may be run at a pressure of from about 50 psi to5000 psi, with 500 psi to 1500 psi being preferred.

The amount of hydrogen provided for contact with the olefinic startingmaterial (either by addition of HI or by feed of H₂ gas) shouldrepresent at least one molecule of hydrogen for each olefinic bond to besaturated, and is preferably 10 times said minimum, or less (i.e., themolar ratio of hydrogen available for reacting to olefinic startingmaterial is preferably between 10:1 and 1:1). When hydrogen gas is used,the hydrogen can be fed either in the pure state or diluted with aninert gas (e.g., nitrogen, helium or argon).

The dihydropolyfluoroalkanes of this invention include thedihydropolyfluoropentane represented by the structural formula CF₃CHFCHFCF₂ CF_(3;) the dihydropolyfluorohexane represented by thestructural formula CF₃ CHFCHFCF₂ CF₂ CF_(3;) and thedihydropolyfluoroheptanes represented by the structural formulae CF₃ CF₂CHFCHFCF₂ CF₂ CF₃ and CF₃ CHFCHFCF₂ CF₂ CF₂ CF₃.

A process is provided in accordance with this invention for preparing alinear dihydropolyfluoroalkane selected from the group consisting of CF₃CHFCHFCF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₃, CF₃ CF₂ CHFCHFCF₂ CF₂ CF₃, CF₃CHFCHFCF₂ CF₂ CF₂ CF₃, and CF₃ CF₂ CHFCHFCF₂ CF₃, which comprises thestep of reacting an olefinic starting material in the vapor phase withhydrogen over a Group VIII metal catalyst. Preferably the catalyst isfrom the palladium group. The olefinic starting material for thisprocess has the same number of carbon atoms as the desireddihydropolyfluoroalkanes and is selected from the group consisting ofCF₃ CF═CFCF₂ CF₃, CF₃ CF═CFCF₂ CF₂ CF₃, CF₃ CF₂ CF═CFCF₂ CF₃, CF₃ CF₂CF═CFCF₂ CF₂ CF₃, and CF₃ CF═CFCF₂ CF₂ CF₂ CF₃ ; and has its olefinicbond between the carbon atoms which correspond to the carbons which bearthe hydrogen in said dihydropolyfluoroalkane.

Unsupported metal catalysts and supported metal catalysts wherein themetal is palladium, rhodium, or ruthenium are particularly suitable foruse in this process. Supports such as carbon or alumina may be employed.Supported palladium catalysts are preferred.

The vapor phase reduction can be carried out at temperatures in therange of from about 50° C. to about 250° C.; the preferred temperaturerange is from about 100° C. to about 200° C. The pressure of thehydrogenation may vary widely from less than 1 atmosphere to 20 or moreatmospheres. The molar ratio of hydrogen to olefinic starting materialfor this process is preferably between about 0.5:1 and 4:1, and is morepreferably between about 0.5:1 and 1.5:1.

Another process is provided in accordance with this invention forpreparing a linear dihydropolyfluoroalkane selected from the groupconsisting of CF₃ CHFCHFCF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₃, CF₃ CF₂CHFCHFCF₂ CF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₂ CF₃, and CF₃ CF₂ CHFCHFCF₂ CF₃,which comprises the step of reacting an olefinic starting material inthe liquid phase with hydrogen over a Group VIII metal catalyst(preferably from the palladium group); wherein said olefinic startingmaterial has the same number of carbon atoms as saiddihydropolyfluoroalkane and is selected from the group consisting of CF₃CF═CFCF₂ CF₃, CF₃ CF═CFCF₂ CF₂ CF₃, CF₃ CF₂ CF═CFCF₂ CF₃, CF₃ CF₂CF═CFCF₂ CF₂ CF₃, and CF₃ CF═CFCF₂ CF₂ CF₂ CF₃ ; and wherein saidolefinic starting material has its olefinic bond between the carbonatoms which correspond to the carbons which bear the hydrogen in saiddihydropolyfluoroalkane.

Palladium and rhodium are the preferred metals, with palladium being themost preferred. The metal catalysts may be supported, for example, oncarbon or on alumina, with carbon the preferred support.

The liquid phase reduction can be carried out at temperatures rangingfrom about 0° C. to 200° C., with a preferred range being from about 25°C. to about 100° C. The pressure of the hydrogenation may vary widelyfrom less than 1 atmosphere to 30 atmospheres or more. The molar ratioof hydrogen to olefinic starting material for this process is preferablybetween about 1:1 and 100:1 and is more preferably between about 1:1 and10:1.

This hydrogenation is preferably carried out in the absence of a polarsolvent. The reduction may be carried out neat (i.e., using no solventor diluent) or in the presence of a non-polar solvent. Suitablenon-polar solvents which may be employed include inert low dielectricalkanes (e.g., nonane and, cyclohexane) or low dielectric aromatics(e.g., toluene, benzene and orthoxylene)

Another process is provided in accordance with this invention forpreparing a linear dihydropolyfluoroalkane selected from the groupconsisting of CF₃ CHFCHFCF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₃, CF₃ CF₂CHFCHFCF₂ CF₂ CF₃, CF₃ CHFCHFCF₂ CF₂ CF₂ CF₃, and CF₃ CF₂ CHFCHFCF₂ CF₃,which comprises the step of reacting an olefinic starting material whichhas the same number of carbons as said dihydropolyfluoroalkane and isselected from the group consisting of CF₃ CF═CFCF₂ CF₃, CF₃ CF═CFCF₂ CF₂CF₃, CF₃ CF₂ CF═CFCF₂ CF₃,CF₃ CF₂ CF═CFCF₂ CF₂ CF₃, and CF₃ CF═CFCF₂ CF₂CF₂ CF₃, at an elevated temperature with hydrogen in the presence of atleast one material selected from the group consisting of iodine andhydrogen iodide or with hydrogen iodide. The olefinic starting materialshould have its olefinic bond between the carbon atoms which correspondto the carbons which bear the hydrogen in the desireddihydropolyfluoroalkane.

Iodine and/or HI is used for this hydrogenation in accordance with theteachings of U.S. patent application Ser. No. 07/533,333. Hydrogeniodide for the reaction may be provided by several methods. For example,the reaction may be run with stoichiometric HI. Alternatively, thereaction may be run with catalytic amounts of HI in the presence ofhydrogen. The reaction may also be run with hydrogen using catalyticamounts of iodine. This latter method is preferred for batch reactionsand for ease of handling. This reaction may be accomplished in theabsence of supported metal catalysts; and indeed the catalyst for thisreaction typically consists essentially of iodine and/or hydrogeniodide. The reaction temperature for this reaction should generally befrom 100° C. to 500° C. A preferred temperature range is from 200° C. to400° C. This reaction may be run at a pressure of from about 50 psi to5000 psi, with 500 psi to 1500 psi being preferred.

The amount of hydrogen provided for contact with the olefinic startingmaterial (either by addition of HI or by feed of H₂ gas) shouldrepresent at least one molecule of hydrogen for each olefinic bond to besaturated, and is preferably 10 times said minimum, or less (i.e., themolar ratio of hydrogen available for reacting to olefinic startingmaterial is preferably between 10:1 and 1:1). When hydrogen gas is used,the hydrogen can be fed either in the pure state or diluted with aninert gas (e.g., nitrogen, helium or argon).

The processes of this invention wherein the olefinic starting materialis hydrogenated over a palladium group metal catalyst, allow forselecting between processes wherein the major product (i.e., above 50mole percent based upon the amount of olefinic starting materialhydrogenated) is a dihydropolyfluoroalkane, and processes wherein themajor product is a trihydropolyfluoroalkane. In particular, liquid phaseprocesses wherein polar solvents are used favor the production oftrihydropolyfluoroalkanes and may thus be used to producetrihydropolyfluoroalkanes as the major product. In a preferred process,where high yield of trihydropolyfluoroalkanes is desired, a liquid phaseprocess using polar solvents may be used to produce about 65 molepercent or more trihydropolyfluoroalkane product. Examples 1, 2, 4, 7,10 and 15 herein are referenced as examples of trihydrononafluoropentanepreparation

On the other hand vapor phase processes, neat liquid phase processes,and liquid phase processes using non-polar solvents (i.e., processesessentially free of polar solvents) favor production ofdihydropolyfluoroalkanes and may thus be used to producedihydropolyfluoroalkanes as the major product of the reaction. In apreferred process, where high yield of dihydropolyfluoroalkanes isdesired, a vapor phase process, a neat liquid process, or a liquid phaseprocess using non-polar solvents may be used to produce about 65 molepercent or more dihydropolyfluoroalkane product. Examples 5, 6, 8, 9,11, 12, 13 and 14 herein are referenced as examples ofdihydropolyfluoroalkane preparation. Examples 13 and 14 indicate furtherthat the use of an appropriate solvent can result in the formation ofone diastereomeric dihydro compound selectively. Example 8 illustratesthe high selectivity for introduction of two hydrogens which is possiblein a vapor phase reaction using a palladium catalyst.

The processes of this invention which do not use metal catalysts andwhich react olefinic starting material with hydrogen in the presence ofiodine and/or hydrogen iodide or with hydrogen iodide, allow forproducing as the major product a polyfluoroalkane wherein exactly twohydrogens have been added to said olefinic starting material. In apreferred process, where high yield of polyfluoroalkane wherein exactlytwo hydrogens have been added to an olefinic starting material isdesired, the processes using iodine and/or hydrogen iodide may be usedto produce about 95 mole percent or more of product wherein exactly twohydrogens have been added to the olefinic starting material. Forexample, 2,3-dihydrodecafluoropentane of over 99% purity can be obtainedby the reaction of one part perfluoropentene-2 with excess hydrogen andabout 0.5 part of iodine at 300° C. and 1000 psi for 20 hours (seeExample 3 herein).

The dihydro and trihydro linear polyfluoropentanes, polyfluorohexanesand polyfluoroheptanes of this invention are useful as solvents(especially those compounds having boiling points of 100° C. or less).They are replacements for currently environmentally suspectchlorofluorocarbons such as trichlorotrifluoroethane. They have zeroozone depletion potential. They are nonflammable. Thesepolyfluoroalkanes may be used by themselves or in combination with othermiscible solvents as cleaning agents or defluxing agents for solidsurfaces, for example, printed wire boards. The compounds having boilingpoints above 75° C. are useful as vapor degreasers. The compounds ofthis invention may also be used as drying agents.

The dihydropolyfluoroalkanes and trihydropolyfluoroalkanes of thisinvention are miscible with various solvents conventionally used incleaning operations. Compositions suitable for use in cleaningoperations can be prepared which comprise a mixture of dihydro- and/ortrihydropolyfluoroalkanes of this invention with one or more compoundsselected from the group consisting of alcohols, ethers, esters, ketones,nitromethane, acetonitrile, and halogenated hydrocarbons. The preferredalcohols and halogenated hydrocarbons contain from 1 to 4 carbon atoms;the preferred ethers contain from 2 to 6 carbon atoms; and the preferredesters and ketones contain from 3 to 6 carbon atoms. Examples ofsuitable alcohols include methanol, ethanol and isopropanol. Examples ofsuitable ethers include tetrahydrofuran and diethylether. Examples ofsuitable ketones include acetone and methylethylketone. Examples ofsuitable halogenated hydrocarbons include methylene chloride (i.e.,dichloromethane), 1,1,2 -trichloro-1,2,2 -trifluoroethane,dichlorodifluoroethane, trichloroethene, and trans-1,2-dichloroethylene.Preferably, such compositions contain at least about 5 percent by weighttotal of the polyfluoroalkanes of this invention; and can contain up to99 percent by weight, or even more thereof. Preferred compositionsinclude mixtures of CF₃ CHFCHFCF₂ CF₃, CF₃ CH₂ CHFCF₂ CF₃ or CF₃ CHFCH₂CF₂ CF₃ (especially CF₃ CHFCHFCF₂ CF₃) with one or more of saidalcohols, ethers, esters, ketones, nitromethane, acetonitrile andhalogenated hydrocarbons. Most preferred with respect to ozone depletionpotential are compositions in which no component contains chlorine.

The mixtures of this invention are useful in a wide variety of processesfor cleaning solid surfaces which comprise treating said surfacetherewith. Applications include removal of flux and flux residues fromprinted circuit boards contaminated therewith.

Compositions which comprise an admixture of effective amounts of one ormore of the dihydropolyfluoroalkanes and trihydropolyfluoroalkanes ofthis invention with one or more solvents selected from the groupconsisting of alcohols, ethers, esters, ketones, nitromethane,acetonitrile and halogenated hydrocarbons to form an azeotrope orazeotrope-like mixture are considered especially useful. Reference ismade to U.S. patent application Ser. No. 07/595,833 (see U.S. Pat. No.5,064,559 which issued pursuant thereto) and to U.S. patent applicationSer. No. 07/595,834 (see U.S. Pat. No. 5,064,560 which issued pursuantthereto) for providing examples of certain azeotrope admixtures. Inparticular, azeotropic compositions consisting essentially of about 95.3weight percent CF₃ CHFCHFCF₂ CF₃ and about 4.7 weight percent methanol(boiling point about 39.9° C.); consisting essentially of about 97.1weight percent CF₃ CHFCHFCF₂ CF₃ and about 2.9 weight percent ethanol(boiling point about 43.4° C.); consisting essentially of about 97.4weight percent CF₃ CHFCHFCF₂ CF₃ and about 2.6 weight isopropanol(boiling point about 45.5° C.); consisting essentially of about 60.5weight percent CF₃ CHFCHFCF₂ CF₃, about 36.2 weight percent trans1,2-dichloroethylene, and about 3.3 weight percent methanol (boilingpoint about 35.3° C.); and consisting essentially of about 63.9 weightpercent CF₃ CHFCHFCF₂ CF₃, about 35.1 weight percent trans1,2-dichloroethylene and about 1.0 weight percent ethanol (boiling pointabout 35.1° C.) are considered useful for cleaning printed circuit boardcontaminated with flux and flux-residues.

The compositions of the invention may be used in conventional apparatus,employing conventional operating techniques. The solvent (s) may be usedwithout heat if desired, but the cleaning action of the solvent may beassisted by conventional means (e.g., heating, agitation, etc.) . Insome applications (e.g., removing certain tenacious fluxes from solderedcomponents) it may be advantageous to use ultrasonic irradiation incombination with the solvent(s).

Compositions provided in accordance with this invention can be used incleaning processes such as is described in U.S. Pat. No. 3,881,949 andU.S. Pat. No. 4,715,900, both of which are incorporated herein byreference.

The mixtures of the instant invention can be prepared by any convenientmethod including mixing or combining the desired amounts of thecomponents. A preferred, method is to weigh the desired amounts of eachcomponent and thereafter combine them in an appropriate container.

Practice of the invention will become further apparent from thefollowing non-limiting examples.

EXAMPLE A

Preparation of CF₃ CF═CFCF₂ CF₃ (F-Pentene-2)

A 400-mL metal tube charged at -20° C. with 8.0 g of AlF₂.8 Cl₀.2(prepared from AlCl₃ +CFCl₃), 75 g (0.50 mol) of hexafluoropropene, and50 g (0.50 mol) of tetrafluoroethylene was shaken for 30 min. while thetemperature rose quickly to 20° C. and the pressure dropped to 8 psi.Distillation of the product afforded 88.0 g (70%) of F-pentene-2, b.p.23°-26° C., identified by IR, NMR and GC/MS. NMR showed the product tobe 89% trans-isomer and 11% cis-isomer.

EXAMPLE 1 Reduction of Perfluoro-pentene-2 (F-pentene-2; CF₃ CF═CFCF₂CF₃)

A 1-L metal tube charged with 86 g (0.34 mol) of F-pentene-2,300 mL ofabsolute ethanol, and 5 g of 5% Pd on carbon was agitated at 25° C.under 50-100 psi of hydrogen until the pressure drop was 0 after 14 hr.The tube was cooled to 0° C., gases were bled, and the cold reactionmixture was pressure-filtered under N₂. Distillation gave product, bpmainly 43°-46° C. which co-distilled with a small amount of ethanol. Thecrude product contained trihydrononafluoropentane (2 isomers) anddihydrodecafluoropentane in a weight ratio of about 77:23. After a waterwash to remove ethanol, the product (59 g) was dried over MgSO₄,filtered and fractionated . A foreshot, bp 27°-28° C., was shown by ¹ Hand 19_(F) NMR to be a mixture of cis- and trans-F-pentene-2, Z-CF₃CH═CFCF₂ CF₃, and Z-CF₃ CF═CHCF₂ CF.sub. 3. This was followed by 37 g ofcuts, bp 46°-53° C., increasingly rich in F-2H, 3H-pentane andcontaining less F-2H, 2H, 3H-pentane and F-2H,3H,3H-pentane.Identification was by GC/MS and NMR.

The product mixture of this example was shown (by further exposing it tohydrogen in the presence of a Pd/C catalyst) to be stable to reductionconditions once it is formed, indicating that loss of F⁻ or HF leadingto trihydro product occurs while the olefin is reacting on the catalystsurface.

EXAMPLE 2 Reduction of CF₃ CF═CFCF₂ CF₃

A 500 mL heavy-walled bottle charged at 0° C. with 4 g of 5% Pd oncarbon catalyst, 150 mL of absolute ethanol, and 145 g (0.58 mol) ofperfluoropentene-2 was attached to a Parr hydrogenation apparatus andpressured to 50 psi with hydrogen. The reaction mixture was shaken at25° C. and occasionally repressured with hydrogen until the rate ofpressure drop had greatly slowed (8 hr). Distillation gave 130.1 g of aforeshot rich in product, bp 26°-77° C., which was combined with 58.1 gof foreshot from a similar reduction of 77 g (0.308 mol) ofperfluoropentene-2, washed with 100 mL of water, dried over CaCl₂,filtered, and distilled. The product so obtained, bp 49°-51° C., 128.3g, was shown by GC to consist of about 82 wt-% of trihydro derivativesCF₃ CH₂ CHFCF₂ CF₃ CF₃ CHFCH₂ CF.sub. 2 CF₃ and 18 wt-% of CF₃ CHFCHFCF₂CF₃, the latter composed of two diastereomers in 96:4 ratio. Analysis byproton NMR indicated 84 mol-% of trihydro derivativesperfluoro-2H,2H,3H-pentane and perfluoro-2H, 3H, 3H-pentane in 86:14ratio, along with 16 mol-% of perfluoro-2H,3H-pentane diastereomers.

EXAMPLE 3 Reduction of CF₃ CF═CFCF₂ CF₃

A metal rocker tube charged with 97.4 g (0.384 mol) of iodine and 191.8g (0.767 tool) of perfluoropentene-2 was cooled, evacuated, pressuredwith 100 psi of hydrogen, and heated to 300°C. Hydrogen pressure wasraised to 1000 psi and maintained there while the vessel was kept at300° C. for 1 day. The vessel was cooled to 5° C., gases were vented,and the cold product (157.2 g, 99% pure by GC) was washed with coldaqueous Na₂ S₂ O₃, dried over Na₂ SO₄, to give perfluoro-2H,3H-pentane,bp 43°-52°C., as two diastereomers in 49:51 ratio.

EXAMPLE 4 Reduction of CF₃ CF═CFCF₂ CF₃

A Parr hydrogenator charged cold with 6.0 g of 0.5% Pd on aluminaspheres, 20.4 g (0.082 tool) of perfluoropentene-2, and 100 mL ofabsolute ethanol was purged three times with N₂ and pressurized to 45psi with hydrogen. The mixture was shaken for 12 hours at 25° C. whilehydrogen pressure was maintained at 25-45 psi, by which time the rate ofpressure drop was slow. Distillation gave a foreshot, 2 5 g, boilingbelow 30° C., followed by 16.7 g of crude product, bp 32°-77° C. Thedistillate was shown by GC and NMR analyses to be composed of 5% ofunreacted perfluoropentene-2, 26% of the olefinsperfluoro-2H-pentene-2/perfluoro-3H-pentene-2, 64% of perfluoro-2H, 2H,3H-pentane and perfluoro-2H, 3H, 3H-pentane, and 13% of perfluoro-2H,3H-pentane. Thus the ratio of trihydro- to dihydropentanes was 83:17. Itis expected that this ratio would be higher if the monohydroolefins werefurther reduced.

EXAMPLE 5

Reduction of Neat Liquid CF₃ CF═CFCF₂ CF₃

A mixture of 2.0 g of 5% Pd on carbon and 22.7 g (0.091 tool) ofperfluoropentene-2 was agitated under 30-45 psi of hydrogen at 25° C.for two hours, after which hydrogen absorption slowed. The liquidproduct was shown by GC and NMR to contain an 83:17 ratio of dihydro-totrihydropentanes, with the perfluoro-2H,3H-dihydropentane present as twodiastereomers in 90:10 ratio. Only 1% of the total product was unreactedperfluoropentene-2.

EXAMPLE 6

Reduction of Neat Liquid F-Heptenes

Reduction of 44.2 g (0.126 mol) of perfluoroheptene-3/perfluoroheptene-2mixture in a Parr hydrogenator with 2.8 g of 5% Pd on carbon at 25° C.proceeded readily at 20-50 psi of hydrogen. GC and MS indicated 3.5% ofthe crude product to be unreacted perfluoroheptenes, the rest being an87:13 ratio of dihydro- to trihydropolyfluoroheptanes. Fractions of theproduct, bp 85°-94° C., were shown by NMR to containperfluoro-3H,4H-heptane and perfluoro-2H,3H-heptane, in addition to theexpected trihydro derivatives.

EXAMPLE 7 Reduction of CF₃ CF═CFCF₂ CF₃

A heavy-walled Parr bottle charged with 2.0 g of 5% Pd on carbon, 20.7 g(0.083 mol) of perfluoropentene-2, and 100 mL of dry DMF was kept under20-50 psi of hydrogen while being shaken at 25° C. for 3 hours, afterwhich time hydrogen absorption had nearly ceased. The mixture wastreated with 4.2 g of NaF and distilled to give 17.6 g of crude product,bp 47°-48° C., After a wash with cold water and drying over CaCl₂, therewas obtained. 16.1 g (83%) of trihydrofluoropentanes as an 81: 19mixture of perfluoro-2H, 2H, 3H-trihydropentane and perfluoro-2H, 3H,3H-trihydropentane, identified by GC and NMR. NMR also indicated thepresence of 4 mol-% of perfluoro-2H,3H-dihydropentane and 1 mol-% ofperfluoro-2H, 3H,3H-tetrahydropentane.

This reaction provided a preferred polar solvent for very selectivelyreducing perfluorinated linear internal olefins to trihydro derivativeswith hydrogen and metal catalyst under mild conditions.

EXAMPLE 8 Vapor Phase Reduction of CF₃ CF═CFCF₂ CF₃

A 6"×1/2" O.D. Hastelloy tube was charged with 10.0 g of 0.5% palladiumon 5×8 mesh alumina spheres. This was a commercial sample from Calsicatwhich was reduced with hydrogen prior to use. Co-fed to the reactor werevaporized perfluoropentene-2 (2 mL/hr as liquid) and hydrogen (20mL/min). Product stream leaving the reactor was analyzed by on-line GCand on-line MS, the product then being collected in a -80° C. trapduring the run. At temperatures of 100-°200° C., conversions were 96-99%with yields of perfluoro-2H, 3H-pentane consistently 95% or better overthe temperature range. The level of trihydro by-product was ˜1%.Product, bp 50°-55° C., easily obtained pure by a simple fractionation,was shown by GC and NMR analyses to have a ratio of diastereomers ofabout 90:10.

EXAMPLE 9 Reduction of CF₃ CF═CFCF₂ CF₃

Example 8 was substantially repeated except that the catalyst was 5.0 gof 1% ruthenium on carbon and the operating temperature was 200° C.Under these conditions perfluoropentene-2 conversion was 41.2% and thecombined selectivity to the perfluoro-2H,3H-pentane isomers was 70.4%.

EXAMPLE 10 Reduction of CF₃ CF═CFCF₂ CF₃

A Parr bottle charged with 100 mL of methanol was blanketed withnitrogen while 2.0 g of 5% Pd on carbon was added, then cooled to 0° C.while 22.6 g (0.090 mol) of perfluoropentene-2 was added. The coldreactor was connected to the hydrogenation apparatus, purged three timeswith nitrogen, then pressured to 48 psi with hydrogen. The mixture wasshaken at 25° C. for 4 hours while the hydrogen pressure was maintainedat 12-48 psi; during this time the pressure dropped rapidly and thenleveled. Calcium chloride (20 g) was added to the reaction mixture, andcrude product was distilled, bp 45°-54°C. The distillate was washed withice water and dried over anhydrous CaCl₂ to give 17.9 g (85%) oftrihydropolyfluoropentanes, identified by GC and MS, and shown by NMR tobe an 80:20 mixture of perfluoro-2H, 2H, 3H-trihydropentane andperfluoro-2H, 3H, 3H-trihydropentane. NMR also indicated the presence ofabout 3 mol-% perfluoro-2H,3H-dihydropentane and about 4 mol-% ofperfluoro-2H, 2H, 3H, 3H-tetrahydropentane

This reaction demonstrated the high selectivity for formation oftrihydro derivatives from linear, internal perfluoroolefins which can beachieved by carrying out a metal-catalyzed reduction in a polar liquidphase.

EXAMPLE 11 Reduction of Neat CF₃ CF═CFCF₂ CF₃

A chilled Parr bottle was charged with 2.05 g of 5% Rh on carbon, and21.0 g (0.084 mol) of perfluoropentene-2, and was pressured to 50 psiusing H₂. The mixture was shaken at 25° C. under 30-50 psi of H₂ untilhydrogen uptake ceased (about 11 hours). The crude product was indicatedby GC to contain 81% perfluoro-2H, 3H-pentane (88:12 diastereomerratio), and 19% trihydrononafluoropentanes, and was distilled from CaCl₂to give 13.7 g of product, bp 46°-53° C. NMR showed the composition tobe 77% dihydro/23% trihydropentanes.

EXAMPLE 12 Reduction of Neat CF₃ CF═CFCF₂ CF₃

Reduction of 20.9 g (0.08 mol) of perfluoro-pentene-2 and 10 g of 0.5%Pd on alumina was carried out at 25° C. under 30-50 psi of hydrogen over13 hours. The resulting product was indicated by GC to contain a 72:28ratio of dihydro- to trihydropolyfluoropentanes, with theperfluoro-2H,3H-pentane present as diastereomers in 94:6 ratio.

EXAMPLE 13 Reduction of CF₃ CF═CFCF₂ CF₃

A 500 mL Parr hydrogenator bottle was charged with 2.0 g of 5% Pd oncarbon, 100 mL of nonane, and 20.9 g (0,084 tool) of perfluoropentene-2,pressured to 47 psi with hydrogen, and shaken at 25° C. for 6 hourswhile hydrogen pressure was maintained at 11-47 psi. Distillationafforded 16.5 g, bp 47°-53° C., indicated by NMR to contain dihydro- andtrihydropentanes in 73:27 ratio, with perfluoro-2H,3H-pentane present astwo diastereomers in 93:7 ratio.

EXAMPLE 14 Reduction of CF₃ CF═CFCF₂ CF₃

Reduction of 22.7 g (0,091 tool) of perfluoropentene-2 with 2.0 g of 5%Pd on carbon in 100 mL of toluene was carried out at 25° C. under ca.20-50 psi of hydrogen until hydrogen absorption fell to 0.3 psi/hour.Distillation served to isolate volatiles, bp 25°-b 62° C., 18.3 g, whichcontained 65 wt-% of pentanes composed of 94:6 mol-ratio of dihydro- totrihydropentanes. The perfluoro-2H, 3H-pentane consisted ofdiastereomers in a 97:3 ratio, an especially high selectivity.

This reaction demonstrated the unusually high selectivity fordihydrogenation of a perfluorinated linear internal olefin and, inaddition, striking selectivity for formation of only one diastereomericdihydro product, when the metal-catalyzed reduction is carried out in anonpolar medium.

EXAMPLE 15 Reduction of CF₃ CF═CFCF₂ CF₃

A reactor containing 20.0 g (0.080 mol) of perfluoropentene-2, 2.0 g of5% Pd on carbon, and 100 mL of acetic acid was maintained under 30-50psi of hydrogen while being shaken at 25° C. for 26 hours. Distillationafforded 10.1 g of liquid, bp 46°-55° C., which was little changed by awash with ice-water. GC and NMR analyses indicated a 66:34 ratio oftrihydropolyfluoropentanes to dihydropolyfluoropentanes.

Particular embodiments of the invention are included in the Examples.Other embodiments will become apparent to those skilled in the art froma consideration of the specification or practice of the inventiondisclosed herein. It is understood that modifications and variations maybe practiced without departing from the spirit and scope of the novelconcepts of this invention. It is further understood that the inventionis not confined to the particular formulations and examples hereinillustrated, but it embraces such modified forms thereof as come withinthe scope of the following claims.

What is claimed is:
 1. A process for preparing a lineartrihydropolyfluoroalkane selected from the group consisting of CF₃ CH₂CHFCF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₃, CF₃ CH₂ CHFCF₂ CF₂ CF₃, CF₃ CHFCH₂ CF₂CF₂ CF₃, CF₃ CF₂ CH₂ CHFCF₂ CF₃, CF₃ CHFCH₂ CF₂ CF₂ CF₂ CF₃, CF₃ CH₂CHFCF₂ CF₂ CF₂ CF₃, CF₃ CF₂ CHFCH₂ CF₂ CF₂ CF₃, and CF₃ CF₂ CH₂ CHFCF₂CF₂ CF₃, comprising the step of: reacting an olefinic starting materialin the liquid phase with hydrogen over a metal catalyst from thepalladium group in the presence of a polar solvent; wherein saidolefinic starting material has the same number of carbon atoms as saidtrihydropolyfluoroalkane and is selected from the group consisting ofCF₃ CF═CFCF₂ CF₃, CF₃ CF═CFCF₂ CF₂ CF₃, CF₃ CF₂ CF═CFCF₂ CF₃, CF₃ CF₂CF═CFCF₂ CF₂ CF₃ and CF₃ CF═CFCF₂ CF₂ CF₂ CF₃ ; wherein said olefinicstarting material has its olefinic bond between the carbon atoms whichcorrespond to the carbons which bear the hydrogen in saidtrihydropolyfluoroalkane; wherein said olefinic starting material ishydrogenated over a palladium catalyst at a temperature in the range offrom about 0° C. to about 200° C.; wherein the molar ratio of hydrogento olefinic starting material is between 1:1 and 100:1; and wherein saidlinear trihydropolyfluoroalkane is the major product of saidhydrogenation.
 2. A process according to claim 1 wherein CF₃ CH₂ CHFCF₂CF₃ is prepared and wherein CF₃ CF═CFCF₂ CF₃ is reacted with hydrogen.3. A process according to claim wherein CF₃ CHFCH₂ CF₂ CF₃ is preparedand wherein CF₃ CF═CFCF₂ CF₃ is reacted with hydrogen.
 4. A processaccording to claim 1 wherein CF₃ CH₂ CHFCF₂ CF₂ CH₃ is prepared andwherein CF₃ CF═CFCF₂ CF₂ CF₃ is reacted with hydrogen.
 5. A processaccording to claim 1 wherein CF₃ CHFCH₂ CF₂ CF₂ CF₃ is prepared andwherein CF₃ CF═CFCF₂ CF₂ CF₃ is reacted with hydrogen.
 6. A processaccording to claim 1 wherein CF₃ CF₂ CH₂ CHFCF₂ CF₃ is prepared andwherein CF₃ CF₂ CF═CFCF₂ CF₃ is reacted with hydrogen.
 7. A processaccording to claim 1 wherein CF₃ CF₂ CH₂ CHFCF₂ CF₂ CF₃ is prepared andwherein CF₃ CF₂ CF═CFCF₂ CF₂ CF₃ is reacted with hydrogen.
 8. A processaccording to claim 1 wherein CF₃ CF₂ CHFCH₂ CF₂ CF₂ CF₃ is prepared andwherein CF₃ CF₂ CF═CFCF₂ CF₂ CF₃ is reacted with hydrogen.
 9. A processaccording to claim 1 wherein CF₃ CH₂ CHFCF₂ CF₂ CF₂ CF₃ is prepared andwherein CF₃ CF═CFCF₂ CF₂ CF₂ CF₃ is reacted with hydrogen.
 10. A processaccording to claim 1 wherein CF₃ CHFCH₂ CF₂ CF₂ CF₂ CF₃ is prepared andwherein CF₃ CF═CFCF₂ CF₂ CF₂ CF₃ is reacted with hydrogen.
 11. A processaccording to claim 1 wherein the temperature is from about 25° C. toabout 100°C.
 12. A process according to claim 1 wherein the molar ratioof hydrogen to olefinic starting material is between about 2:1 and 10:1.13. A process according to claim 1 wherein the polar solvent is selectedfrom the group consisting of water, alcohols, glycol, acetic acid,dimethyl formamide, N-methyl pyrollidone, triethylamine and mixturesthereof.
 14. A process according to claim 1 wherein the catalyst issupported.